java 断点下载

 1 package com.my9yu.manager.module.test;
 2 
 3 import java.io.File;
 4 import java.io.IOException;
 5 import java.io.InputStream;
 6 import java.io.RandomAccessFile;
 7 
 8 import org.apache.http.HttpEntity;
 9 import org.apache.http.HttpResponse;
10 import org.apache.http.client.ClientProtocolException;
11 import org.apache.http.client.HttpClient;
12 import org.apache.http.client.methods.HttpGet;
13 import org.apache.http.impl.client.DefaultHttpClient;
14 
15 public class TestHttp {
16     public static void main(String[] args) throws ClientProtocolException, IOException {
17         String url = "http://dl_dir.qq.com/music/clntupate/QQMusic_Setup_85_850.exe";
18         String downFile = "d:\\QQMusic.exe";
19         Long netFileLenght = getNetFileSize(url);
20         Long localFileLenght = getLocalFileSize(downFile);
21 
22         if (localFileLenght >= netFileLenght) {
23             System.out.println("已下载完成");
24             return;
25         }
26 
27         System.out.println("netFileLenght : " + netFileLenght + " localFileLenght : " + localFileLenght);
28         final HttpClient httpClient = new DefaultHttpClient();
29         httpClient.getParams().setIntParameter("http.socket.timeout", 5000);
30 
31         final HttpGet httpGet = new HttpGet(url);
32         httpGet.addHeader("Range", "bytes=" + localFileLenght + "-");
33 
34         final HttpResponse response = httpClient.execute(httpGet);
35         final int code = response.getStatusLine().getStatusCode();
36         final HttpEntity entity = response.getEntity();
37         System.out.println(code);
38 
39         if (entity != null && code < 400) {
40 
41             File file = new File(downFile);
42             RandomAccessFile randomAccessFile = new RandomAccessFile(file, "rw");
43             randomAccessFile.seek(localFileLenght);
44 
45             InputStream inputStream = entity.getContent();
46             int b = 0;
47             final byte buffer[] = new byte[1024];
48             while ((b = inputStream.read(buffer)) != -1) {
49                 randomAccessFile.write(buffer, 0, b);
50             }
51 
52             randomAccessFile.close();
53             inputStream.close();
54             httpClient.getConnectionManager().shutdown();
55             System.out.println("下载完成");
56         }
57     }
58 
59     public static Long getLocalFileSize(String fileName) {
60         File file = new File(fileName);
61         return file.length();
62     }
63 
64     public static Long getNetFileSize(String url) {
65         Long count = -1L;
66         final HttpClient httpClient = new DefaultHttpClient();
67         httpClient.getParams().setIntParameter("http.socket.timeout", 5000);
68 
69         final HttpGet httpGet = new HttpGet(url);
70         HttpResponse response = null;
71         try {
72             response = httpClient.execute(httpGet);
73             final int code = response.getStatusLine().getStatusCode();
74             final HttpEntity entity = response.getEntity();
75             if (entity != null && code == 200) {
76                 count = entity.getContentLength();
77             }
78         } catch (ClientProtocolException e) {
79             e.printStackTrace();
80         } catch (IOException e) {
81             e.printStackTrace();
82         } finally {
83             httpClient.getConnectionManager().shutdown();
84         }
85         return count;
86     }
87 }